Method and apparatus for marking objects in a pile

ABSTRACT

A method and an apparatus for making e.g. boardlike objects ( 11 ) arranged in a pile ( 12 ), in which method the objects are marked with a marking printed by a print head ( 26 ) and containing e.g. information about the object. To improve the marking quality, the objects are pressed together to reduce or eliminate gaps between them in the direction of compression, and the marking is made on an edge of the object that is parallel to the direction of compression of the objects.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/FI02/00432 which has an Internationalfiling date of May 21, 2002, which designated the United States ofAmerica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and to an apparatus formarking e.g. boardlike objects in a pile.

2. Description of Background Art

In the manufacture of various board products, such as e.g. chipboards,the board may be provided with a marking giving information such asmanufacturer, type, date of manufacture of the board or the like. Thereare systems in which such a marking is made in an individual board, e.g.on an edge of the board. Systems are also known in which the marking ismade on the edge of the boards while the boards are in a pile. Themarking is produced using e.g. an ink jet print head or equivalent.

A drawback regarding the marking of boards is that the piles of boardsmay have air gaps between boards due e.g. to bending of the boards, aconsequence of which is e.g. that the text is not always printed in theright place in the printing area and that the printing ink used for themarking may spread between the boards, staining the surface of theproduct. Because of the gaps, the height dimension of the pile isundeterminable.

SUMMARY AND OBJECTS OF THE INVENTION

The object of the present invention is to achieve a new type of methodand apparatus for marking objects in a pile that make it possible toavoid the drawbacks of prior art.

The invention is mainly characterized in that, according to theinvention, the boards in the pile of boards are pressed togetherespecially to eliminate errors caused by air gaps between the boards. Ina solution according to the invention, pressure is applied from the topof the pile of boards by using a pressing element that compresses thepile of boards by its own weight. In this situation, the pile is e.g. ona conveyor at a marking station.

In more definite terms, the invention is characterized by what ispresented in the claims.

The invention makes it possible to achieve a substantial improvement ofthe print quality. In addition, the invention allows the pile height tobe more accurately determined in the printing station because air gapsbetween boards have been eliminated.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in detail by the aidof an embodiment example with reference to the attached drawings,wherein

FIG. 1 presents a pack of boards provided with a marking on one edge ofthe boards, and

FIG. 2 presents a marking station comprising a pressing device accordingto the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows chipboards 11 arranged one over the other as a pile 12.Printed on an edge 13 of each board 11 is a marking 14 consisting ofinformation such as type, size, manufacturer, date of manufacture of theboard and similar data. The pile 12 of boards may consist of a pluralityof boards placed on top of each other, and its height may typically bee.g. about 1 m. In addition, the pile may comprise e.g. protectiveboards placed under and over it.

The pile of boards 12 is brought e.g. on a chain conveyor 21 (FIG. 2) toa marking station 22, where a marking as shown in FIG. 1 is made on theedge of each board. The station consists of a frame part 23, a printerunit 24 controlling the printing, and a system, e.g. a PLC system (notshown in the figure) used for controlling the movable parts of themarking station. Fitted in the frame part 23 are guide bars 25permitting motion in the directions of the three principal axes x, y, z,with a print head 26, e.g. an ink jet print head fitted on the guidebars, and actuators 27 for moving and guiding the print head indirections x, y, z at a suitable short distance from the edge of thepile 12 e.g. during a marking operation.

In addition to this, the frame part is provided with vertical guide bars28 with a pressing element 30 fitted on them and moved vertically bymeans of an electric motor drive and cogged belts 29. The pressingelement 30, typically weighing 100-150 kg, compresses the pile of boardsfrom above in its edge area while the pile is on the conveyor. For thispurpose, the electric drive is provided with a freewheel clutch mountede.g. on its shaft, allowing the pressing element 30 to be first loweredwith a restrained movement against the upper surface of the pack ofboards 12 and then released so that it exerts a pressure on the pile ofboards by its own weight. The movements of the pressing element arecontrolled by the control unit (not shown in the figure).

It is obvious to the person skilled in the art that the invention is notlimited to the embodiment described above, but that it may be variedwithin the scope of the following claims. The compression of the pile ofboards can also be effected using e.g. a hydraulic or pneumatic cylinderor similar actuating devices and their combinations. The pack of boardsmay also be compressed e.g. by placing a fixed stop above the pack andlifting the pack from below against the top stop e.g. by means of ascissor table. The pack may also be compressed by pressing itsimultaneously from both the lower and upper surfaces and so on. Thesphere of application of the invention is not limited to boardlikeobjects; instead, it can also be applied in the case of other objects ofsuitable shape.

1. A method for marking objects arranged in a pile, comprising the stepsof: pressing together and compressing the objects in the pile from aboveby means of a weight of a pressing element; marking the objects with amarking printed by a print head, the marking containing informationabout the objects, wherein the pressing step reduces or eliminates gapsbetween the objects in the direction of compression, and wherein themarking step makes the marking on an edge of the objects that isparallel to the direction of compression of the objects.
 2. The methodaccording to claim 1, wherein in the pressing step a pressing element ismoved vertically by a motor drive, which, using a freewheel clutch, iscaused to release the pressing element upon reaching an upper surface ofthe pile.
 3. The method for marking objects according to claim 1,wherein the objects are boards.
 4. An apparatus for marking objectsarranged in a pile, comprising: a pressing unit for compressing theobjects to reduce or eliminate gaps between the objects in a directionof compression in order to improve marking quality; and a print head formarking the objects with a marking containing information about theobjects, wherein the pressing unit includes a pressing element forpressing the pile from above by its own weight, and wherein the printhead is fitted to make the marking on edges of the objects that areparallel to the direction in which the objects are compressed.
 5. Theapparatus according to claim 4, further comprising: vertical guide barson which the pressing element is mounted; and a motor drive, by means ofwhich the pressing element is moved vertically along the guide bars, themotor drive being provided with a freewheel clutch by means of which thepressing element is released upon reaching an upper surface of the pile.6. The apparatus according to claim 4, wherein the pressing unit is apress beam.
 7. The apparatus for marking objects according to claim 4,wherein the objects are boards.
 8. An apparatus for marking objectsarranged in a pile, comprising: a pressing unit having a pressingelement for compressing the objects to reduce or eliminate gaps betweenthe objects in a direction of compression in order to improve markingquality; vertical guide bars on which the pressing element is mounted; amotor drive, by means of which the pressing element is moved verticallyalong the vertical guide bars, the motor drive being provided with afreewheel clutch by means of which the pressing element is released uponreaching an upper surface of the pile; and a print head for marking theobjects with a marking containing information about the objects, whereinthe print head is fitted to make the marking on edges of the objectsthat are parallel to the direction in which the objects are compressed.9. The apparatus for marking objects according to claim 8, wherein thepressing unit includes a pressing element for pressing the pile fromabove by its own weight.
 10. The apparatus for marking objects accordingto claim 8, wherein the pressing unit is a press beam.
 11. The apparatusfor marking objects according to claim 8, wherein the objects areboards.